Purification of chlorocarbons



Patented Dec. 11, 1951 PURIFICATION OF CHLOROCARBONS Patrick Anthony Florio, Woodside, and John Douglas Calfee, Manhasset, N. Y., assignors to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York No Drawing. Application October 16, 1948,

7 Serial No. 55,024

13 Claims. (Cl. 260-654) This invention relates to the purification of the chlorocarbons, CC12=CC12 and C014. More particularly, the invention is directed to the purification of such compounds obtained by chlorinolysis (i. e. high temperature exhaustive chlorination resulting in the rupture of the carbon to carbon bond) of 1,1-difluoroethanes such as ethy1idene fluoride.

In certain processes involving elevated temperature chlorinolysis of 1,1-difluoroethanes such as CHsCHFz, and fractionation of the chlorinolysis reaction product, substantial yields of CC12=CC12 and CCL; are obtained. These chlorocarbons, after recovery in crude form from the chlorinolysis reaction mixture, contain as impurities small but nevertheless deleterious amounts of chemically active organic fluorine containing materials, in particular hydrolyzable chlorofluoroethylenes such as CCl2=CClF. The products, CC12=CC12 and C014, are in demand for use as dry-cleaning solvents and have important commercial applications provided they are in a form suificiently pure. The boiling points of the troublesome organic fluorine containing materials are sufliciently close to those of CC12=CC12 and 0314 to render purification by fractionation difficult and expensive to carry out commercially. In particular, one of the chlorofluoroethylenes normally obtained in appreciable amounts, CCl2=CClF, boils at a temperature (71 C.) sufliciently close to that of the CCli (77 C.) to render complete separation of these two materials quite diflicult. Further, the boiling point of CC12=CC1F is near enough to the boiling point of CC12=CC12 (121 C.) so that separation of the last small traces of this impurity from the CC12=CC12 by fractionation is not feasible. Impure chlorocarbons produced by chlorin-v olysis of Ll-diiiuoroethanes may contain chemically active organic fluorine containing compounds (such as hydrolyzable chlorofiuoroethylcues) in amount such that the fluorine content is substantially greater than 0.02 weight per cent. For example, crude CC12=CC12 may contain chlorofluoroethylene impurities in quantity such that the fluorine content is as much as 0.2% or more, and in the case of crude CCli, the corresponding fluorine value may be even higher.

These chemically active fluorine compound impurities even when present in the chlorocarbon in these very small quantities undergo slow hydrolysis and/or oxidation upon standing resulting in the evolution of acidic materials including HF and/or H01, and impart a pungent, phosgenic odor to the chlorocarbon. The hydrolysis or oxidation products thus evolved also cause serious corrosion of glass or metal containers in which the chlorocarbon is stored. These properties are undesirable, particularly from the standpoint of using the CC12=CC12 and C014 as dry-cleaning solvents.

Purification of CC12=CC12 and C014 heretofore produced by non-chlorinolysis prior art processes has presented different problems due to. the different nature of the impurities to be removed. Accordingly, it has been found necessary to devise other improved methods for the purification of CCl2=CCl2 and C014 formed by chlorinolysis of 1,1-difluoroethanes, and it is an object of this invention to afford procedures to accomplish this purpose. For some uses of the subject chlorocarbons, it may be desirable merely to effect substantial reduction of the content of chemically active fluorine containing materials. For otheruses where specifications are stringent, it may be necessary to reduce content of these impurities to a degree such that the fluorine content of the chlorocarbon is less than .02 percent, and objectionable odor and corrosiveness of the chlorocarbons are substantially absent. Accordingly, it is a particular object of the invention to produce chlorocarbons meeting these specifications.

We have found that the purification of the: chlorocarbons CC12=CC12 and CCh containing as impurity such fluorine containing materials, e. g. CCl2=CClF, which chlorocarbons arepreferably those which may be obtained by chlorinolysis of a 1,1-difluoroethane, may be effected by subjecting the chlorocarbon to the action of an inorganic oxygenated silicon compound. By such procedure, hereinafter more fully described, if desired the fluorine content may be reduced advantageously to less than .02%, and the objectionable odor and the corrosive characteristics of the subject chlorocarbons may be removed.

The agents which are effective in the purification of chlorocarbons according to our invention are inorganic oxygenated silicon compounds which may be any form of silica per se (SiOz) or which contain silica in free or chemically combined form. For example, silicic acid is a preferred agent. It is known that silicic acid exists in manyv forms each differing chemically from the other in the degree of hydration, i. e. the amount of water found in the molecule. Beginning with ortho-silicic acid, H4Si04, one may progressively remove waterfrom the molecule, obtaining with each dehydration step a different dehydration derivative of silicic acid, and eventually, substantially pure silica. Thus, ortho-silicic acid or any of the dehydration derivatives thereof may be employed as purification agents. Commercially obtainable silica gel is another preferred purifying .temperature and other factors;

agent. Glass wool, granulated or ground glass or diatomaceous earth may also be employed to advantage. Aluminum silicate, and calcined clays may be employed. The presence of moderate amountsofiree water in the treating. agents does not appear deleterious; All of the foregoing materials, e. g., silica, silicic acids, silicates and mixtures thereof, are particularly active in eifecting the ob ectives of the invention.

Although not essential to successful practice of our invention, it is advantageous to employ treating agent in a form whichzhas-a-largesurface exposed to the chlorocarbon undergoing treatment, e. g. silicic acid in pellets or powder.

form, silica gel in pellet or granular-f0rm,,and glass or non-activated silica, aluminum silicate, calcined clays and diatomaceous earth in ground or finely divided form are suitable for :applica tion to our process.

- Thecamount-of purifying agent to be employed in. proportion to-the amount of chlorocarbon un-- dergoing treatment may vary considerably according to the particular agent, the state of subdivision of the agent, the degree of agitation andturbulence. in the liquid being processed, the

Some destruction of undesirablekorgnanic fluorine containing material is obtained with very small amounts of purifying agent, e'. g. 1-2 weight percent or less based on the weight of the liquid material being treated. On the other hand, although to noiparticular advantage, very large amounts of agent of'the order of 50 percentormore may be'employed without adversely affecting either the chlorocarbon or the silicon compound. Usually, we find that; adequate purification can be obtained when the amount of treating agent used is about 3-15 weight percent: of' the body of chlorocarbon. undergoing treatment. Ordinarily consumptionof the agentsduring thezpurification A operation is negligible; and .hence' the agent may be recovered and usedrepea'tedly wlth'outnoticeable decrease in effectiveness;

The temperature at which :the chlorocarbon is subjected to the 1 action of the :silicon "compound may'vary over wide-limits. Toobtain rapidity of reaction, we usually employelevatedtemperat'ures, i. e.;above 50C. and :below those temperatures 'at-rwhioh decomposition of the chlorocarbon undergoing treatment begins. We find, however, that at temperatures above 60 C. reaction rates sufficiently high for economical operation may be obtained while temperatures above 150 C. are ordinarily of insubstantial additional benefit, and accordingly temperatures in therange 60 C. to 150C. are suitable. To facilitate contact ofthe chlorocarbon undergoing treatment with the purifying agent, it is desirable to agitate the liquid. Such agitation may be obtained by stirring or by employing other'well known means. A particular procedure for carrying out the invention is to boil; undersubstantially 100% reflux conditions, abod'y of-the chlorocarbon liquor containing thepur-ify ing agent. In this manner of operation, adequate treatment temperature and agitation may be had simultaneously.

The pressure maintained during the treating operation may be anything desired or suitable. If, as in the above procedure, the chlorocarbon is subjectedto boiling, the pressure maintained may be that at which the material boils at the desired temperature"which should not exceed the decomposition temperatureof the particular chlorocarbon.

The timeof treatment may vary according to the temperature, the amount of chemically active organic fluorine containing impurity present, the degree of purification desired, and to some extent upon the particular silica compound employed, and itsstate of subdivision. some destruction of undesired material may be effected in only a few minutes, but more usually 2 to 4 hours are allowed. For any particular impure chlorocarbon starting material and any particular set of operating conditions, time of contact to eifectthe. desired degree of purification may be determined by making suitable test operations and determining:corrosiveness, odor and fluorine content'of the product.

As, heretofore mentioned its is preferable to conduct the purification under treating agenttemperature-time conditions which yield a product having less than .02% fluorine, negligible pungent phosgenic odor-and negligible corrosive effect. Accordingly, for a given purifying agent and temperature, heatingtime is prolonged until.

a test sample shows a fluorine content of 0.02% or less. Corrosiveness may be determined .by placing a small sample of chlorocarbon in a glass container and maintaining the containerat 50 C. Chlorocarbon showing imperceptible corrosive attack when stored indefinitely under these conditions may be obtained according to preferred embodiments of our invention, whereas impure chlorocarbon produces a visible attack on the glass in 12 hours.

The manner in which the treating agents bring about the removal of undesirable fluorine compounds in the process of our invention is not known to us. We believe that the agents cause destruction, i. e. chemical decomposition of these impurities. It is possible that hydrolysis of the fluorine compounds is effected or the fluorine compoundsare otherwise destroyed liberating HF while the purifying agent is simultaneously converted by the HF to silicon halides or silicon oxyhalides. However, we do not intend to limit our invention to any particular mechanism of reaction or theory of operation of the purifying agent.

While particular embodiments of our invention heretofore described comprise treating the chlorocarbonin batch processes, our invention isnot limited to batchwise operation. Chlorocarbon may be subjected to the action of the purifying agent in continuous processes, e. g. by passing the chlorocarbon to be treated through a pipe or other conduit packed with silicon compound treating agent maintained at the desired treatins temperature. In such operation, the desired agi tation may be obtained by turbulence of liquid flow.

Following the treating operation heretofore described, the reaction mixture is cooled and the treating agent is separated from the chlorocar bon by well known mechanical means such as filtration or decantation. Thereafter the material obtained is jfractionated and the purified,

chlorocarbon recovered. During the, treatment of thechlorocarbon, somezacidic materail such as: HCl or HF may be formed. These acidic materials may be separated by the fractionation procedure, but according to a particular embodiment of the invention we effect separation subsequent to the removal of the silicon compound from the chlorocarbon and prior to the fractionation. According to the latter procedure we first decant supernatant liquid from the treating agent, then remove acidic materials by extraction or neutralization, then remove any water present in the material, and finally subject the material to fractionation to recover purified chlorocarbon. Water or other aqueous media are suitable for extraction of acids. If it is desired to neutralize the acids, solid neutralizing agents such as soda ash or liquid agents such as aqueous alkaline solutions may be employed. The chlorocarbons may be dehydrated by drying over calcium chloride. a

The treatment of the chlorocarbon may be car'- ried out in a vessel made of any of the usual materials of construction which resist attack by HF and HCl. We prefer apparatus constructed of bonded graphitic material such as is commonly known as Karbate.

In accordance with a modification, the process of the invention may be carried out in an apparatus comprising a boiling pot and a superjacent column which may be packed in suitable manner with the purifying agent to be used. In the practice of this modification, the liquor in the pot is boiled, vapors rise into the column and into contact with the purifying material. The overhead vapors are condensed and returned as reflux to the column. According to this practice, chlorocarbon undergoing treatment is simultaneously contacted in the form of vapor and liquid (condensate) streams, preferably countercurrently, with the treating agent at temperatures heretofore described. Preferably, the column is operated under conditions of high (e. g. substantially 100%) reflux to afford adequate time interval for treatment. The HF and HCl acidic materials may be bled out of the top of the column during or subsequent to refluxing, and thereafter the acid-free treated chlo'robanbon may be recovered. Alternatively, after suitable treatment of chlorocarbon vapor and liquid with silicon compound, the HF and H01 may be distilled overhead simultaneously with thechlorocarbon, and separated therefrom by subsequent distillation procedures.

The following examples are illustrative of our invention, the parts being by weight: I

Example 1.-A crude product from the chlorinolysis of CH3CI-IF2 was fractionally distilled and a fraction boiling in the range l'15 -12 2 C. was recovered. This material contained essentially CCl2=CCl2 and chemically active organic fluorine containing materials. It had a pungent, phosgenic odor, when stored at 50 C. in a glass container, caused visible attack on' the glass in 24 hours, and contained 0.07% fluorine by analysis. parts of partially dehydrated silicic acid in powder form, sold commercially as silicic acid were added to 100 parts of this fraction'and the mixture was refluxed at atmospheric pressure for 4 hours. Following contact with the silicic acid, the CC12=CC12 was cooled, the silicic acid separated bydecantation, and the liquid washed with a dilute solution of sodium hydroxide and with water. It was then dried over calcium chloride and fractionally distilled. 90 parts" of CC12==CC12 boiling over the range 120.5 to l21.0 C. were recovered which had no pungent phosgenic odor and did not attack glass when'held were placed in the still pot and refluxed through thedistillation column for a period of minutes after which time distillate was collected. After drawing off and discarding a small foreshots fraction, 180 parts of distillate were collected which had no pungent odor and did not attack glass when held for hours at 50 C. in a glass container. The fluorine content of the purified material was less than 0.02%.

. Example 3.--5 parts of calcined clay (aluminum silicate) were added to 100 parts of the fraction described in Example land the mixture was re-.- fluxed at atmospheric pressure for 4 hours. Following contact with the clay the CC12=CC12 was cooled, the clay separated by decantation and filtration and the liquid washed with a dilute solution of sodium hydroxide and with water. It was then dried over calcium chloride and frac tionally distilled. 92 parts of CC12=CCI2 boiling over the range 119.8 to 120.5 C. were recovered which had no pungent phosgenlc odor and did'not attack glass when held for hours at 50 C. in a glass container. The fluorine con-- tent of the purified material was less than 0.02%.

Example 4.--5 parts by weight of finely subdivided glass were added to 100 parts of the fraction described in Example 1 and the mixture was refluxed at atmospheric pressure for 2 hours. Following contact with the glass the CC12='CC12 was cooled, allowed to remain overnight at room temperature, the glass separated by decantation, and the liquid washed with a dilute solution of sodium hydroxide and with water. It was then dried over calcium chloride and fractionally distilled. 90 parts of CC12=CC12 boiling over the range 120.5 to 121.0" C. were recovered which had no pungent phosgenic odor and did not attack glass when held for hours at 50 C. in a glass container. The fluorine content of the purified material by chemical analysis was less than 0.02%.

Example 5.An impure carbon tetrachloride contained about 0.49% by weight of CCl2=CClF (0.07% fluorine by analysis), had a pungent phosgenic odor and when stored in a glass container at 50 C. caused visible attack on the glass in 24 hours. 100 parts of this material were mixed with 5 parts of silicic acid of the type described in Example 1 and then refluxed at atmos pheric pressure for 4 hours. Following contact with the silicic acid, the CO1. was cooled, the silicic acid separated by decantation, and the liquid washed with a dilute solution of sodium hydroxide and with water. It was thendried over calcium chloride and fractionally distilled. parts of C014 boiling over the range of '75 to 76 C. were recovered which had no pungent odor and did not attack glass when held for 85 hours at 50 C. in a glass container. The fluorine content of the purified material was less than 0.02%.

Example 6.5 parts of diatomaceous earth were added to parts of the fraction described in Example 1 andthe mixture was refluxed at atmospheric pressure for 4 hours. Thereafter the CCl2=CCl2 was cooled, the diatomaceous earth separated by decantation, and the liquid washed with d lute solution of sodium hydroxide and with water. It was then dried over calcium thechlor'inolysis of CHi-CHFz, substantially the cameixas employed in- Example 1, which iproduct contalned about 05.5% abytweightbf CGlz -CCIF, and approximately 87% of :which product? boiled in .the range 2116-122" I C., were :charge'd to an-all metal still comprising-.a :steel reboiler-seq'uipped with a steel column. Theilower .portionr' of' the column was packed .with steel Raschig rings,:and the upper portion was packed with'20 .partsi'of silicagel beads. The .crudeproduct was aboiled, overhead vapors were condensedzinaan' externally cooled nickel pipepacked with steelarings, :and substantially all the condensate .was: returned:.as reflux .to the Itop of the column for a' perio'dzof 180 minutes. Thereafter; distillate 'rwas1collected until substantially-all of' the liquid: has:been;:removed from the reboiler. Thee-distillate wasrsubsequently purified by neutralization, awashing, drying and fractionation procedures rdescribedzm Example 1. 89 parts of CCl2=CClz boilingqin-the range, of,120.5 to 121.0 C. were obtained-which hadno'pungent phosgenic odor and did not attack glass when held for-110 hours at 50 C. in aaBlass container. The fluorine content of: the i purified material was less-than 0.02%.

We claim:

1. 'In the purificationiof a C'hlOlOOBJfbOilflOftthB group consisting of CG12=CC12 and C014 containing-asimpurity a chemically active organic (fluorine containing material, the step: of f subjecting said ,chlorocarbon and said fluorine impurity to said chlorocarbon and said fluorine impurity to g the action of an agent of the group consistingof silica, silicic acids, silicates and mixturesvthereof at temperature in the 'range ,ofapproximately 60l50 C. and for a timesufficienttoeffectsubstantial interaction of said impurity withsaid agentand to substantially reduce theisaidimpurity content of said: chlorocarbon, separating the" resulting chlorocarbon :from .said .treat1ng agent, and distilling from \the treated-chlorocarbcn .a purified .product.

-3. .In thepurificationof achlorocarbon of the group consisting of CClz,- CCl2and C014 containingas impurity a chemically activeorganicflum rine containing material, the stepof subjecting saidichlorocarbon. and said fluorine impurityto 1,

the action oft a silicic acidat temperature inithe rangeiof: approximately 50-150 .0. andjona time .sufllcientto eflectgsubstantial,interaotioniofisaid impurity with ,said {silicic acid and-toisubstan ytially reduce ,the said impurity icontentpof-ssaid .chlorocarbon, separating ;the resulting ,chlorocarbon from said treating .agent and ,distilling from-the treated chlorocarbon a,.purifled product.

4. In the puriflcationof.laschlorocarbonsof group consistingof CC12=CC12 and C014- containingas impurity a chemically active;,o 1'ga,nicflue!- :rine c nta n n mate ia h a er o u je n said chlorocarbon and saidi-fluorinet ghnpurity "to gtlieaction of silica gel-.at;temperature ;in.ithe

suflcient cto :eflectfsubstantial interaction: 01:1 impurity with. said. silica, gelaand -to substantially reduce rthesaid impurity content of qsaidr-chlorocarbon, separating, the resulting chlorocarbqn irom;;jsaid treating agent-and. distilling from :the gtreatedk-chlorocarbon :apurified product.

a n5; iInpthe ;1puriflcation of a chlorocarbon ,of the group consisting of CCl2=CC1a and CC'1 containingan organic-fluorine impurity and obtained by .chlorinolysis of a 1,1-difluoroethane, the step -of contacting said chlorocarbon and impurity in? the form of vapor and liquid-streams simultaneously,

with ani-agentof the group-consistingof silica,

silicic acids, silicates and--mixtures thereof at temperature in the range of -150 C.=for,a;time .sufllcientrto efiect substantial interaction ofsaid impurity with said agent-and to-substantiallyrre- ,duce the :said impurity content'of said chlomcarbon; separating the resulting chlorocarbon from saidtreating agent and distilling from the ztreated chlorocarbon-a purified product.

6. Thelprocess of purifying a CCl2=VCClz fraction obtained by -fractionation of achlorinolysis reaction product of a 1,1-difluoroethane, said fraction containingorganic fluorine impurity-in amount greater than 0 .02% by weight of fluorine, which processcomprises contacting said 'fraction with an agent of the group 'COI'lSiStiDKzOf silica, silicic .acids, silicates and mixtures thereof at temperature in the range off-60450 Chtciwa time to effect interaction-of ,said impurity with said agent sufficient to effect ultimate reduction of said impurity contentof said fraction-topless than.0.02% by weight of fluorine, removingrsald treating agent from said CClz=CClz fraction and distilling from said fraction a purified CCl2=CCh product containing less than 002% by weightof fluorine.

1'7. The process of purifying a CGl2=CClz"fraction obtained by fractionation-of the chlorinolysis reaction product of a LI-difluoroethana-said fraction containing organic fluorineimpurity in amount greater than 0.02% by weight of fluorine, which process comprises adding .to said fractiona silicic acid in amount of 3-'-1-5% by weight of said-fraction, heating said fraction in the liquid phase in the presence-of saidsilicic acid at about-theatmospheric boiling temperature of said fraction under substantially "reflux conditions and for atime to eil'ect interaction-of said impurity with said silicic acid sufllcient to ,eflect ultimate-reduction of said impurity-content of said fraction to less'than 0.02 %-by-weight of fluorine, separating said silicic'acid from-said fraction, extracting said fraction with anaqueous .medium and distilling from the silicic acid treated fraction a purified CC12=CC12 product containing' less than 0.02% by weight of fluorine.

' 8; The process of purifying a CCl2=CCl2 fraction obtained 'byfractionation of the chlorinoiysis-*reaction product of a 1,1-jdifluoroethane, said fraction containing-organic fluorine impurity-in amQunt greater than 0.02% by weight of. fluorine. which-5prccess comprisesadding to said fraction "silica gel, in. amount: of 13-15% by weightof said fraction. heating-said fraction in the liquidphaae ;in :the presence ofsaid silica gel atabout theatmospheric boiling temperature of said "fraction x.under substantially 100% reflux conditions and for atime toeflect interaction of-said impurity :with said a silica: l .sufllcient' to efiect r ultimate :reduction of" said impurity .content'ofsaid irac- JilOIljtOdESSqthZH 0.02% "by weight-of fluorine.

separating said silica gel from said fraction-1 exmngecf; ,apprcximately504150 qzandrfonra time ll .tracting saidrfraction: with 'an aqueous medium.

and distilling from the silica gel treated fraction a purified CC12=CC12 product containing less than 0.02% by weight of fluorine.

9. The process of purifying a CC12=CC12 composition obtained by fractionation of the chlorinolysis reaction product of a 1,1-difiuoroethane, said composition containing organic fluorine impurity in amount greater than 0.02% by weight of fluorine, which process comprises the procedure of forming vapors of said composition, condensing part of said vapors, and simultaneously contacting resulting condensate and uncondensed vapors with silica gel at about the atmospheric boiling temperature of said composition, and continuing said procedure for a time to eflect interaction of said impurity with said silica gel suflicient to efiect ultimate reduction of said impurity content of said composition to less than 0.02% by weight of fluorine, separating said composition from said silica gel, and distilling from the separated composition a purified 0012:0012 product containing less than 0.02% by weight of fluorine.

10. The process of purifying a CC12=CC12 composition obtained by fractionation of the chlorinolysis reaction product of a 1,1-difluoroethane, said composition containing organic fluorine impurity in amount greater than 0.02% by weight of fluorine, which process comprises the procedure of forming vapors of said composition, condensing part of said vapors, and simultaneously contacting resulting condensate and uncondensed vapors with a silicic acid at about the atmospheric boiling temperature of said composition, and continuing said procedure for a time to efiect interaction of said impurity with said silicic acid sufiicient to effect ultimate reduction of said impurity content of said composition to less than 0.02% by weight of fluorine, separating said composition from said silicic acid, and distilling from the separated composition a purfled CC12=CC12 product containing less than 0.02% by weight of fluorine.

11. The process of purifying a composition comprising a chlorocarbon of the group consisting of CC12=CC12 and CCLi and containing organic fluorine impurity in amount greater than 0.02% by weight of fluorine, which process comprises contacting said chlorocarbon composition and said impurity with an aluminum silicate at temperature in the range of 60-l50 C. for a time to effect interaction of said impurity with said aluminum silicate suflicient to effect ultimate reduction of said impurity content of said chlorocarbon to less than 0.02% by weight of fluorine, removing said aluminum silicate from said chlorocarbon composition, extracting said composition with an aqueous solvent and distilling from said composition a purified chlorocarbon product containing less than 0.02% by weight of fluorine.

12. The process of purifying a composition comprising a chlorocarbon of the group consisting of CC12=CC12 and C014 containing organic fluorine impurity in amount greater than 0.02% by weight of fluorine, which process comprises contacting said chlorocarbon composition and said impurity with finely divided glass at temperature in the range of -150 C. for a time to effect interaction of said impurity with said glass sufficient to effect ultimate reduction of said impurity content of said chlorocarbon to less than 0.02% by Weight of fluorine, removing said glass from said chlorocarbon composition, extracting said composition with an aqueous solvent and distilling from said composition a purifled chlorocarbon product containing less than 0.02% by weight of fluorine.

13. The process of purifying a composition comprising a chlorocarbon of the group consisting of CC12=CC12 and CCl-i containing organic fluorine impurity in amount greater than 0.02% by weight of fluorine, which process comprises contacting said chlorocarbon composition and said impurity with diatomaceous earth, at temperature in the range of 60-150 C. for a time to efiect interaction of said impurity with said diatomaceous earth sufl'lcient to effect ultimate reduction of said impurity content of said chlorocarbon to less than 0.02% by weight of fluorine, removing said diatomaceous earth from said chlorocarbon composition, extracting said composition with an aqueous solvent and distilling from said composition a purified chlorocarbon product containing less than 0.02% by weight of fluorine.

PATRICK ANTHONY FLORIO. JOHN DOUGLAS CALFEE.

Name Date Britten et a1 June 22, 1937 Number 

1. IN THE PRUIFICATION OF A CHLOROCARBON OF THE GROUP CONSISTING OF CCI2=CCI2 AND CCI4 CONTAINING A IMPURITY A CHEMICALLY ACTIV EORGANIC FLUORINE CONTAINING MATERIAL, THE STEP OF SUBJECTING SAID CHLOROCARBON AND SAID FLUORINE IMPURITY TO THE ACTION OF AN AGENT OF THE GROUP CONSISTING OF SILICA, SILICIC ACIDS, SILICATES, AND MIXTURES THEREOF AT TEMPERATURE IN THE RANGE OF APPROXIMATELY 50150* C., AND FOR A TIME SUFFICIENT TO EFFECT SUBSTANTIAL INTERACTION OF SAID IMPURITY WITH SAID AGENT AND TO SUBSTANTIALLY REDUCE THE SAID IMPURITY CONTENT OF SAID CHLOROCARBON, SEPARATING THE RESULTING CHLOROCARBON FROM SAID TREATING AGENT, AND DISTILLING FROM THE TREATED CHLOROCARBON A PURIFIED PRODUCT. 